Method of making porous metal bearings



Dec. 19, 1944% R. P. KXOEHRING 2,365,

METHOD OF KING POROUS METAL BEARINGS 2 Sfieets-Sheet 1 Filed March 20 Il vwswr'an V Roland P [(aefimby 1115' HT rm vavs Dec. 19, 1944. R. P.KOEHRING I METHOD OF MAKING POROUS METAL BEARINGS .Filed uarcnzo, 1942 Y2 Sfieets-Sheet 2 Hrrnmvss I Patented 1)...19, 1944 METHOD OF, MAKINGPOROUS METAL BEARINGS Roland P." Koehring, Dayton, Ohio, assignor to'General Motors Corporation, Detroit, Mich., a corporation of DelawareApplication March 20, 1942, Serial No. 435,453

3 Claims. (01. 29-1495) This invention relates to a method ofconditioning porous metal articles at the surface thereof and isparticularly concerned with conditiony ing the surface of a porous metalarticle by means of mechanical 'applicatibn of another metal thereto.

An object of the invention is to provide a method and apparatus formechanically forcing particles of metal into the surface pores of theporous metal article during sizing thereof whereby the surface soconditioned approximates the characteristics of the metals which areforced into the pores of the porous metal article.

A further object of the invention is toprovide a method whereby softmetal powders, such as lead, tin, antimony or alloys thereof, in finelydivided form are carried by means of the fluid vehicle, preferably oflubricating character, and wherein said mixture is flowed over thesurface of the porous metal article during the sizing applicationwhereby particles of the soft metal are forced into the pores of theporous metal.

A still further object of the invention is to provide method andapparatus for conditioning the surface of a orous metal article whereina sizing punch is utilized which includes fluid ducts therein that emitsoft metal powder carried by the fluid vehicle during the sizingoperation whereby the soft metal inLthe fluid vehicle is placed directlyin the path. of the sizing punch so that particles ofthe soft metal areimmediately forced into the pores of the porous metal.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accom panyingdrawings wherein preferred embodimens of the present invention areclearly shown.

In the drawings:

Figs. 1 through 4 show one type of apparatus used in carrying out thepresent invention dur ing the steps of the operation on a sphericalmetal bearing; f

Fig. 5 is .an enlarged fragmentary, sectional view of the bearingshowing the conditioned surface thereon;

Figs. 6 through 9 show another type of apparatus in various positionsfor accomplishing the same results wherein a sizing punch is used whichacts-as a means for supplying the metal powder in the lubricant.

- Fig. 10 is an enlarged fragmentary,-sectional shown in Figsj6 through9.

When making" porous metal articles it is desirable to utilizeinexpensive metals and then condition the surface thereof with a moredesirable metal for the purpose intended. An example of such type ofmanufacture is a spherical hearing, such as is used in electric motorsview of the sizing punch used in the apparatus often and the like,wherein the bearing is preferably self aligning,

Spherical bearings therefore rather than form the bearing from bronze itis economical and desirable to utilize porous iron and the like.ventional formulae of iron and graphite, either alone or with a bindingmetal, are formed in the desired shape under pressure and are sinteredunder suitable conditions of time, temperature and atmosphere to form aporous iron-bearing.

' of such alloys being preferably babbitt.

the bronze bearings in certain bearing characteristics as used in manyspecific applications although they are stronger. I. have found thatthese bearing characteristics can be markedly improved so that thebearing is highly suitable for its intended use by effectively liningthe bearing bore with a soft metal powder, for example, 1ead,'tln,antimony, zinc or alloys thereof, one If the lining operationis carriedout by an impregnation step, the cost of the bearing is again increasedso that it is incompatible with the substitution of material. I,therefore, propose to form an effective lining such as the babbitt,simultaneously with the sizing operation.

In the majority of porous metal articles, sizing is resorted to tocompensate for the physicalchanges such as shrinkage which occurs duringthereof wherein a sizing punch of the desired diameter is forced throughthe bore and due to the ductility of the porous metal causes the bore tobecome enlarged to the desired dimensions. This operation canbeaccomplished very well on cupreous articles or ferrous articles.

I have found that if a Babbitt powder, or any other desirable soft metalpowder in a quite finely divided state, for example, 250 mesh, .issuspended in a fluid vehicle, preferably oil although vehicles which arenot lubricating in character can be used with varying degrees of successis supplied around the bearing during the sizing operation, that as thesizing punch passes through the bore of the bearing, particles of thesoft metal are mechanically forced into the sur- J face of the borewhereby the bore of the sized bearing has similar bearingcharacteristics to the soft metal. This bearing surface is highlydesirable since the high portions thereof still remain iron or othermetal whichforms the porous metal bearing and provides a strong loadsupporting structure for the shaft which is to be journaled thereinwhile, the interstices between these high points present a soft metalbearing surface and therefore provide an ideal bearing surface. Bearingsof this type, while carrying are of appreciable size in I order toobtain the bearing surfaces required and For this purpose conhigh loads,do not wear appreciably and therefore are quite desirable.

One form of apparatus which has been used with success is shown in Figs.1 through 4 wherein it illustrates a porous metal bearing which isplaced in a fluid reservoir 22 in a die structure it. positioning pin itin a bath of the liquid vehicle to be used which also includes the softmetal as at id. A punch section 30, having a contour similar to the diesection 24, is provided through which a sizing punch 32 is passed. Afterthe bearing to is in position, as shown in Fig. l, the punch section illdescends and clamps the spherical bearing in place, as shown in Fig. 2,in which position the bore of the bearing is filled with the fluidvehicle with the soft metal powder in suspension. The sizing punch itnext passes through the bore and presses the pin it downwardly wherebythe soft metal lining is impressed upon the surface of the bore of thebearing. Punch section Jill is removed together with the sizin punch itand the bearing is then forced upwardly on the die portion as shown inFig. t whereupon the hearing may be removed. It is desirable to form thepositioning pin with a valve therein, designated at M which includes aspring at so that the fluid vehicle and metal powder may be replenishedtherethrough.

Another type of the apparatus is shown in Figs. 6 through 9 wherein adie section llll is providcd which has a movable center portion ll whichincludes a semi-spherical die cavity M therein which is suitable forreceiving the bushing lll. Preferably the upper portion of the diecavity llll is filled with a liquid lubricant carrying finely dividedsoft metal powder. Punch section it also includes a semi-sphericalcavity which is adapted to fit over the bearing and likewise carryingthe sizing punch M which is slidable therein. its shown in Fig. 7 afterthe bearing is in place the punch section it is moved downwardl and thenthe sizing punch 52 is passed through the bearing, as shown in Fig. 8.Whereupon the section t8 and sizing punch 52 are removed and the movableportion 12 of the die is forced upwardly so that the bearing 20 may beremoved. In this particular apparatus the sizing punch provides themeans for supplying lubricant and the soft metal powder to the bearingbore.

Fig. 10 shows a sectional view of this punch wherein a central duct 58is provided within the punch which communicates by means of a pluralityof apertures 58 at various stages of the sizing rings on the punch. Thefluid vehicle with the soft metal powder is forced through the duct 56and outwardly through the apertures 58 so that it flows directly intothe path of the moving sizing punch whereby the soft metal powder isrndintained in the desired position at all times. Valve mechanism isalso provided in this form for removingexcess liquid from the die cavityas is required. In both embodiments the valve 34 may be balanced byadjustment of spring 35 to cause varying degreesof hydraulic pressure tobe exerted on the fluid vehicle and metal powder suspended therein. Inthis manner, as the burrushing punch descends, pressure is applied whichforces the fluid vehicle into the pores of the bearing and therebyeffectively filters out a layer of soft metal powder on the surface ofthe bore,

The bearing is preferably set over a' aaoases which powder is furtherforced into the pores of the porous metal by the burnlshlng action ofthe punch.

From the foregoing it is apparent that I have provided a facile methodfor effectively changing the frictional characteristics of the rubbingsurface of a porous metal article. It is likewise apparent thattreatment on a flat article may be made in a like manner, the mainfeature in the invention being that the pressure is applied to force thesoft metal particles carried in fluid vehicles into the pores of themetal article while sliding in a plane parallel to the surface treated.It is also possible that the surface of the article maybe treated withsome other metal which does not necessarily improve the frictionalcharacteristics if such a surface is desired and it is to be understoodthat all such expedients come within the scope of my invention.

While the embodiments of the present invention as herein disclosed,constitute preferred forms. it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. In a method of effectively lining the bore of a porous metal bearingwith soft metal powder and simultaneously impregnating the bearing withoil and sizing the bore thereof, the steps comprising: providing aporous metal bearing having a bore therein of a diameter slightly lessthan a diameter ultimately desired, providing a sizing punch of thedesired diameter and greater than the diameter of said bore, forcingsoft metal powder and oil into the pores of the bearings andsimultaneously sizing the bearing bore by forcing .said punch throughsaid bore while simultaneously supplying soft metal powder suspended inoil to the bore ahead of said punch.

52. The method of improving the bearing characteristics of a porousmetal bushing, comprising the steps of providing a porous metal bushingformed from slntered metal powders and having a bore therein of adiameter less than the diameter ultimately desired, providing a sizingpunch having a diameter substantially the diameter ultimately desired insaid bushing bore, immersing said bushing in oil having fine particlesof soft metal suspended therein, forcing said punch through said boreand ultimately forcin said soft metal powder into the surface pores ofsaid bushing bore.

3. The steps in a method of providing a soft metal lining at the bore ofa porous bearing and simultaneously sizing the bore of said bearing to adiameter substantially that desired comprising: providing a. porousmetal bearing having a bore therethrough of substantially less diameterthan the diameter ultimately desired, providing a. sizing punch havingsubstantially the diameter desired ing bore by movement of said punchthrough the bearing bore whereby an effective soft metal lining isprovided at the bearing bore and the bore isslzed to the diameterultimately desired.

ROLAND P. KOEHRING.

